ABSTRACT
<p><b>OBJECTIVE</b>To establish an exonuclease protection mediated polymerase chain reaction (PCR) assay for the non-radioactive, sensitive detection of the binding of protein and DNA.</p><p><b>METHODS</b>The 1 pmol/L-10 nmol/L 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) dissolved in dimethyl sulphoxide (DMSO), was added into 100 microl SD rat hepatic cytosol in vitro, which contained different amount of aromatic hydrocarbon receptors (AhR) and relative proteins, and ligand-AhR-DRE complex were formed in addition to 1 fmol/L-100 nmol/L DNAs probes containing the sequence of DRE. With the digestion of Exonuclease III and S1 nuclease, free DNAs were digested to oligonucleotide and binding DNA remained due to protein (AhR) protection and be amplified by PCR. The results of PCRs were shown by loading on 2% agarose electrophoresis. DMSO was used as negative control and blank control was set up.</p><p><b>RESULTS</b>Target DNA (285 bp) could be observed in the ligand groups, but not in the control group. The minimal amount of receptor was 2.5 fmol/L and the minimal amount of DNA probes was 2 fmol.</p><p><b>CONCLUSIONS</b>Exonuclease protection mediated PCR assay should be a good non-radioactive tool to quantify the interaction of protein and DNA with high sensitivity and simplicity.</p>